Due to the growing importance of olefin metathesis, a great need exists for providing suitable catalysts, which beneficially perform at industrial scale. A considerable number of organometallic alkylidene catalysts is already known to homogeneously catalyze olefin metathesis. Although it is further known that in general heterogeneous catalysts may be easier separated off from reaction mixtures than homogeneous catalysts, e.g. by filtration, which is an advantage particular at industrial scale, comparatively few heterogeneous catalysts have been accessible for olefin metathesis. Exemplarily, in the following, known heterogeneous tungsten catalysts are briefly discussed:
WO3 on SiO2 may be used for metathesis reactions; however, such catalysts typically operate at rather elevated temperatures. E.g., http://handle.net/10413/896 describes the performance of a WO3/SiO2 catalyst for the metathesis of 1-hexene in an isothermal, gas-phase fixed bed tubular reactor between 420 and 500° C.
Mazoyer, E. et al. report the synthesis of an alkyl oxo tungsten derivative supported on silica as olefin metathesis catalyst (Chem. Commun. 2010, 46, 8944-8946). Herein, (tBuCH2)3XWO (X=alkyl, halogen, alkoxide, . . . ) was reported to react with silica, pretreated at 700° C., to give (≡SiO)(tBuCH2)2Cl(W═O) and/or (≡SiO)(tBuCH2)3(W═O), although a targeted alkylidene structure was (≡SiO)(tBuCH2)X(W═O)(═CHt-Bu) (X═Cl or CH2tBu). However, said supported catalyst works at relatively high temperature, i.e. >100° C., and the actual nature of the active site is unknown.
Rhers et al., Organometallics, 2006, vol. 25, 3554, disclose the formation of ethene and butenes, including 1-butene, from propene in a self-metathesis reaction catalyzed by a silica supported tungsten catalyst. The catalyst has been characterized as syn-[(—SiO)(W(═NAr)(═CHtBu)(CH2tBu)] (Ar=2,6-iPrC6H3) of following formula:

F. Blanc et al., Proc. Natl. Acad. Sci. USA, Aug. 26, 2008, vol. 105, no 34, 12123-12127, later disclose the selective formation of ethene and 2-butene from propene in a self-metathesis reaction by a silica supported tungsten catalyst. This reaction is a heterogeneously catalyzed. The catalyst is of the following structure:
and is prepared by grafting [W(═N(2,6-diisopropylphenyl)(═CHtBu)(2,5-Me2C4H2)2] on SiO2-(700).
WO 2015/049047 relates to supported tungsten catalysts of the general formula(≡SiO)xW(═O)(═CR1R2)(R3 or R4)2-x,wherein each of R1 and R2 is independently R, —OR, —SR, —N(R)2, —OC(O)R, —SOR, —SO2R, —SO2N(R)2, —C(O)N(R)2, —NRC(O)R, or —NRSO2R; each R is independently hydrogen or an optionally substituted group selected from C1-20 aliphatic, C1-20 heteroaliphatic having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, phenyl, ferrocene, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl ring, a 5-6 membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 4-7 membered saturated or partially unsaturated heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 7-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or: two R groups on the same nitrogen atom are taken together with the nitrogen to form an optionally substituted 3-12 membered saturated, partially unsaturated, or aryl ring having 0-5 additional heteroatoms not including the same nitrogen atom independently selected from nitrogen, oxygen, or sulfur; or: two R groups on the same oxygen atom are taken together with the oxygen to form an optionally substituted 3-12 membered saturated, partially unsaturated, or aryl ring having 0-5 additional heteroatoms not including the same oxygen atom independently selected from nitrogen, oxygen, or sulfur; R3 and R4 have independently the same meaning as R1 and R2; or tris(C1-20 alkyl)silyl, tris(C1-20 alkyl)silyloxy, tris(C1-20 alkoxy)silyl, tris(C1-20 alkoxy)silyloxy, tris(aryl)silyl, tris(aryl)silyloxy, tris(aryloxy)silyl, or tris(aryloxy)silyloxy; and wherein x=1 or 2.
WO 2015/162245 A2 relates to metal alkylidene N-heterocyclic carbene complexes of general Formulas (A) to (D)
wherein A1 stands for NR2 or PR2, A2 stands for CR2R2′, NR2, PR2, O or S, A3 stands for N or P, and C stands for a carbene carbon atom, ring B is an unsubstituted or a mono or poly-substituted 5 to 7-membered ring, substituents R2 and R2′ stand, inter alia, for a linear or branched C1-C10-alkyl group and, if A1 and A2 each stand for NR2 or PR2, are the same or different, M in Formulas (A), (B), (C) or (D) stands for Cr, Mo or W, X1 or X2 in Formulas (A) to (D) are the same or different and represent, inter alia, C1-C18 carboxylates and C1-C18-alkoxides, Y is inter alia oxygen or sulfur, Z is inter alia a linear or branched C1-C10-alkylenoxy group, and R1 and R1′ in Formulas (A) to (D) are, inter alia, an aliphatic or aromatic group. Ring B may be coupled via a spacer to a solid support such as glass, zirconia, titania, silica or polymer organic support materials, e.g. based on poly(methacrylates) or polystryrene/polydivinylbenzene. The compounds are suitable for use as catalysts for olefin metathesis reactions and are reported to have the advantage, compared to known Schrock carbene complexes, of displaying clearly increased tolerance to functional groups such as, in particular, aldehydes, secondary amines, nitriles, carboxylic acids and alcohols.
WO 2015/003815 discloses metathesis tungsten catalysts of the following formula
wherein M is W; R1 is H, aryl, heteroaryl, alkyl, or heteroalkyl, optionally substituted, respectively; R2 and R3 can be the same or different and are alkyl, alkenyl, heteroalkyl, heteroalkenyl, aryl, or heteroaryl, optionally substituted, respectively, or hydrogen; R5 is a residue R6—X—, wherein R6 is alkyl, aryl, heteroalkyl, heteroaryl, optionally substituted, respectively; (R7, R8, R9)Si; wherein R7, R8, R9 are independently alkyl, alkoxy, phenyl or phenoxy, optionally substituted, respectively; (R10, R11, R12)C, wherein R10, R11, R12 are independently phenyl, alkyl, optionally substituted, respectively; X═O, S, or NR13, wherein R13 is H; or alkyl or aryl, optionally substituted, respectively; or R5 is R6—CO—NR13, wherein R6 and NR13 have the meaning as defined above, or wherein R6 and R13 taken together form a carbon chain having from 2 to 6 carbon atoms; R5 is a 4 to 8 membered N-containing carbon ring, wherein N is linked to M; and R4 is a residue O—Si(O—)3, and represents silica to which M is linked forming a M—O—Si(O—)3 moiety, preferably wherein silica is comprised in a solid support; under the proviso that a compound in which R1=2,6-diisopropylphenyl, R5 dimethylpyrrol-1-yl, R2=tBu, and R3=H is excluded.